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  <script>
    //翻转数组
    function reverse(arr) {
      if (arr instanceof Array) {
        var newArr = [];
        for (var i = arr.length - 1; i >= 0; i--) {
          newArr[newArr.length] = arr[i];
        }
        return newArr;
      } else {
        return 'error: 你输入的不是数组'
      }
    }

    console.log(reverse([1, 2, 3]));
    console.log(reverse(1, 2, 3));
    //检测是否为数组
    //（1） instanceof 运算符 它可以用来检测是否为数组
    var arr = [];
    var obj = {};
    console.log(arr instanceof Array);
    console.log(obj instanceof Array);
    //（2）Array.isArray(参数);   H5 新增的方法  
    console.log(Array.isArray(arr));
    console.log(Array.isArray(obj));
  </script>
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